High vacuum



A 4 4v 4" l R. M. BYOEHME 2,874,710

HIGH VACUUM Feb. 24, 1959 Filed April 9, I957 l8 INVENTOR.

ATTORNE FIG. 2 Umw Kabul Each; BY

ted S at s Page HIGH VACUUM Robert M. Boehme, Cambridge, Mass, assignor to National Research Corporation, Cambridge, Mass., a corporation of Massachusetts Application April 9, 1957, Serial No. 651,692

' 7 Claims. c1. 137-1 This invention relates to apparatus for pumping a liquid and particularly to electrolytically actuated high vacuum cutoffs.

High vacuum cutoffs of various types, such as conventional mercury-U-type cutoffs, Kenty cutoffs, mercury cutoffs involving the use of some kind of cap or hat, etc. are welleknown in the prior art. Heretofore, however, they have all been subject to rather severe disadvantages. Many prior art cutoffs are incapable of operation against a pressure differential of substantially more than 1 cm. Hg. Another serious disadvantage is the use in many cutoff structures of fragile barometric legs and large, and therefore costly, mercury reservoirs. Further, cutoffs often involve moving parts and/ or the exposure of metallic parts to corrosive materials that may exist within the system. Finally, prior art cutoffs that operate substantially satisfactorily are generally bulky, relatively expensive to produce and maintain, and often require manual control.

Accordingly, it is a principal object of the present invention to provide an improved apparatus for pumping a liquid such as mercury into a device whose operability depends upon the intermittent presence of the liquid.

Another principal object of the instant invention is to provide an improved cutoff for use in a high vacuum system.

Another object of the instant invention is to provide an improved cutoff which will be operative against a pressure differential of approximately one atmosphere.

Another object of the invention is to provide an improved cutoff for use in a high vacuum system which can be operated completely by remote control.

Still another object of the instant invention is to pro- 'vide an improved mercury cutoff which has no moving parts and which exposes no metal, other than mercury, to corros ve substances that may exist within the system.

Still another object of the instant invention is to provide an improved high vacuum cutoff which is relatively compact and inexpensive to produce.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the apparatus possessing the'construction, combination of elements, and arrangement of parts which are exemplified in the following detailed description and the scope of the application of which will be indicated in the claims.

. For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description in conjunction with the accompanying drawings wherein:

Fig. 1 is a diagrammatic, schematic illustration of one embodiment of the invention.

Fig. 2 is a diagrammatic, schematic illustration of another embodiment of the invention.

The present invention is particularly directed to improved apparatus for pumping a liquid into a device requiring the intermittent presence of that liquid in order See to be operable. For convenience of illustration, the invention will be primarily described in connection with an electrolytically actuated mercury cutoff. This specific embodiment is utilized for the purposes of illustration only, and it is not to be construed that the scope of the application is thereby limited.

In the instant invention, the electrolytic decomposition of a liquid such as water is utilized to generate a mixture of gases which displace mercury in a reservoir thereby causing the mercury to rise into a cutoff. In the case of water these gases are hydrogen and oxygen. The height of the mercury head produced can easily be controlled by varying the amount of water electrolyzed. 7 When it is desired to open the cutoff to the flow of gases again, the hydrogen-oxygen mixture is ignited. The water vapor produced immediately condenses and allows the displaced mercury to leave the cutoff and return to its original position.

The advantages of this type of cut-off are numerous. The height of the mercury head produced and the time required to produce it are, for practical considerations, not limited. The cutoff is compact, inexpensive to produce and can be operated by remote control. Also it has no moving parts and exposes nothing to the system on which it acts as a cutoff, other than the mercury itself. Another advantage lies in that, unlike conventional mercury cutoffs, the instant cutoff requires no barometric leg and only a small mercury reservoir; also the height of the mercury in the column is independent of the existing barometric pressure. Further, a power supply of the simplest sort suffices to supply the small amount of D. C. power required.

Referring now to the drawings, there is illustrated in Fig. 1 a schematic, diagrammatic illustration of one embodiment of the invention. A U-shaped cutoff 2 is connected to reservoir 4 by means of re-entrant tube 6. Mercury 8 fills reservoir 4 approximately to level 10. The remainder of reservoir 4 above the mercury level 10 up to level 11 is filled with water 12 containing an electrolyte. The mercury and the water are placed in reservoir 4 by means of tube 14. Reservoir 4 is subsequently sealed off by means of stopcock 16. Two electrodes 18 and 22 project into the water layer 12 in reservoir 4 just above level 10 of the mercury layer. The electrodes are connected to a low voltage D. C. power source (not shown). When the power is turned on, current fiows between the electrodes and electrolysis of the water occurs. The gases released by the electrolysis of the water, which gases constitute a mixture of oxygen and hydrogen, rise to the surface and, as electrolysis continues, increasingly displace the water and mercury layers in reservoir 4. This displacement causes the mercury to rise in the reentrant tube 6 and into the cutoff 2, thereby blocking the cutoff to the passage of gases. Electrolysis continues until either electrode 18 or 22 (or both) are no longer immersed in water, that is, until the water level (as shown by dotted line 24) has fallen below one of the electrodes. When this occurs electrolysis of the water automatically ceases. in the reservoir has fallen to level 28.

When subsequently it is desired to open the cutoff 2 to the flow of gases, the stoichiometric mixture of oxygen and hydrogen in reservoir 4 is ignited to produce water vapor which immediately condenses to water, thereby allowing the displaced mercury to leave the cutoff 2 and return to its undisplaced position in reservoir 4 as shown by level 10. The ignition of the gases is accomplished At this point the mercury level matic diagrammatic illustration of another embodiment of the invention. The general arrangement of components is similar to that illustrated in Fig. 1 and described above except that one of the electrodes is located in the mercury layer 8. With this arrangement of components, the electrolysis of the water layer 12. ceases as soon as the water level has fallen below the electrode 22 as shown by dotted line 26. In this embodiment, the ignition of the hydrogen-oxygen mixture is accomplished by the same means as described above except that the high tension spark is produced between electrode- 22 and the water level 26.

Obviously many changes may be made in the above described apparatus without departing from the scope of the invention. For example, the hydrogen-oxygen mixture produced by the electrolysis of water may be ignited by any suitable means such as a hot platinum filament. Also, even if a high tension spark is utilized for the purposes of ignition as described above, it need not be produced by the discharge of a capacitor. Any other means for producing a high tension spark such as by means of a high voltage transformer is equally suitable for the purposes of the instant invention.

Further, the mixture of gases produced by the electrolysis of a liquid such as water need not be ignited so as to cause an instantaneous and therefore explosive recombination of the gases. By utilizing, for the purposes of initiating the recombination of the gases, a hot filament whose temperature can be closely controlled, the recombination of the gases can be caused to procced slowly and evenly. This phenomena is due to the fact that at a given pressure, there exists a critical temperature below which the hydrogen-oxygen mixture burns rather than explodes. Therefore, by controlling the filament temperature, the rate of recombination of the hydrogen-oxygen mixture can also be controlled.

The explosive mixture can be caused to recombine slowly in another way also. If a suitable gauze such as steel wool is placed about a filament immersed in the explosive gas mixture, and a current subsequently passed through the filament thereby heating it up, the recombination of the gases will be slow and even since combustion of the explosive gases occurs only within the confines of the area described by thesteel wool.

In this way, the rate of combustion of the explosive gas mixture can be greatly retarded and an explosion completely avoided.

Further, although only a standard stopcock is mentioned as a means of placingthe water and electrolyte 1n the reservoir 4, other means such as a check valve, and fritted filter valve are equally suitable for the purposes of the instant invention.

It should be pointed out that the arrangement described above can also be utilized in pumping mercury for use in other high vacuum devices such as Toepler pumps and McLeod gauges.

In this case, the gas mixture produced is preferably vented through stopcock 16 and tube 14 to the atmosphere rather than ignited. Unless a barometric leg is utilized, this embodiment is of course feasible only when operating at above atmospheric pressure. But this em bodiment has the advantage of rendering unnecessary the ignition of large explosive mixtures such as are present when water is the liquid electrolyzed.

When venting explosive mixtures to the atmosphere, however, a suitable wire gauze such as steel wool or copper mesh is preferably placed in the outlet through which the explosive mixture-is vented thereby creating in the outlet an explosive trap which eifectively prevents flashback explosions in the apparatus due to. accidental ignition of the vented gases.

It should additionally be pointed outthat the above described system can also be utilized to pump a liquid.

. to rise.

heavier than, and immiscible with the liquid to be electrolyzed and immiscible alsqwith the liquid to be pumped, is provided between the layer of the liquid to be electrolyzed and the liquid to be pumped as a sort of buffer. For example, if in Fig. 1, a third liquid were placed in tube 6 above the mercury 8, this third liquid would be raised above the mercury when the mercury started The mercury would therefore be acting as a.

butter. In this way any liquid can be raised or lowered to and from a given device providing a suitable buffering the presence of said liquid which comprises, means for providing a reservoir of the liquid to be pumped, said reservoir being sealed from the atmosphere, conduit means connecting said device with said reservoir and extending appreciably into said reservoir means for electrolyzing a portion of said liquid to produce a mixture.

of gases within said reservoir thereby displacing said liquid in said reservoir and causing said liquid to rise into said device, and means for initiating the recombination of said gases to re-form the liquid and thereby allow said displaced liquid to return to said reservoir.

2. Apparatus for raising and lowering a liquid to and from a device the operability of which depends upon the presence of said liquid which comprises, means for providing a reservoir of the liquid to be pumped, said reservoir being sealed from the atmosphere, conduit means connecting said device with said reservoir and extending appreciably into said reservoir means for electrolyzing a portioin of said liquid to produce a mixture of gases within said reservoir thereby displacing said liquid'in said reservoir and causing said liquid to rise intosaid device, and means for venting said mixture of gases to the atmosphere thereby allowing said displaced liquid to return to said reservoir.

-3. A process for raising and lowering a liquid to and from a device such as a cutoff which comprises connecting said device to a reservoir containing said liquid, electrolyzing a portion of said liquid within said reservoir to produce a mixture of gases within said reservoir, thereby displacing said liquid in said reservoir and cansing said liquid to rise into said device, and subsequently initiating the recombination of said gasm to re-forrn said liquid and thereby allow said displaced liquid to return to said reservoir.

4. Apparatus for raising and lowering a liquid which is heavier than water but immiscible with water to and from a device the operability of which depends upon the intermittent presence of said liquid in said device, which comprises means for providing a reservoir of-the liquid said reservoir being sealed from the atmosphere, conduit means connecting said device with said reservoir and extending appreciably into said reservoir, means for electrolyzing water within said reservoir to produce a mixture of hydrogen and oxygen within said reservoir, thereby displacing said liquid in said reservoir and cansing said liquid to rise into said device, and means for subsequently igniting said hydrogen-oxygen mixture in order to produce Water vapor which immediately condenses thereby allowing said displaced liquid to return to said reservoir.

5. .Apparatus for raising and lowering a liquid into a device the operability of which depends upon the preseuce of saidliquid which comprises, means for providing areservoir partially fillled with the liquid to be raised andloWered, saidureservoir being sealed from the atmos-' phere, means for providing a layer of a buffer liquid and a second layer of liquid to be electrolyzed in said reservoir, said buffer liquid being heavier than and immiscible with said liquid to be electrolyzed, said buffer liquid also being immiscible with said liquid to be pumped, conduit means connecting said device with said reservoir and extending appreciably into said reservoir means for electrolyzing said liquid to be electrolyzed to produce a mixture of gases within said reservoir, thereby displacing said liquids in said reservoir and causing said liquid to be pumped to rise into said device, and means for subsequently initiating recombination of said gas mixture to re-form the liquid and thereby allow said displaced liquid to return to said reservoir.

6. A valve structure which comprises a cutoff means connected to a mercury-filled tube, said tube being connected to a partially filled mercury reservoir and means for raising said mercury in said reservoir into said cutoif means, said means for raising said mercury comp-rising a layer of electrolyte-containing water above said mercury in said reservoir, means for electrolyzing said water within said reservoir to produce a mixture of hydrogen and oxygen within said reservoir in order to displace said mercury in said reservoir and cause said mercury to rise into said cutoff, and means for subsequently igniting the hydrogen-oxygen mixture to produce water vapor which immediately condenses thereby allowing said displaced mercury to return to said reservoir.

7. Apparatus for raising and lowering a liquid to and from a device the operability of which depends upon the presence of said liquid which comprises means for providing a reservoir of the liquid to be pumped, said reservoir being sealed from the atmosphere, conduit means connecting said device with said reservoir and extending appreciably into said reservoir means for electrolyzing a portion of said liquid to produce a mixture of gases within said reservoir thereby displacing said liquid in said reservoir and causing said liquid to rise into said device, and means for subsequently initiating slow recombination of said gas mixture to slowly re-form the liquid and thereby allow said displaced liquid to slowly return to said reservoir, said ignition means comprising a hot filament surrounded by a suitable gauze.

No references cited. 

